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• how to fill AvFrame pixel by pixel

  18 mai 2017, par masoud khanlo

  i try to encode opengl output to a mp4 file using ffmpeg but when i want to simply fill AvFrame with pixel colors with this code snippet :

  for (y = 0; y < c->height; y++) {
  
  for (x = 0; x < c->width; x++) {
  
      int offset = 3 * (x + y * c->width);
  
  
  
      if (x > 2* c->width / 3 && x width )
  
      {
  
          frame->data[0][offset + 0] = 0; // B
  
          frame->data[0][offset + 1] = 0; // G
  
          frame->data[0][offset + 2] = 255; // R
  
      } 
  
      else if(x < 2 * c->width / 3 && x > c->width / 3) {
  
          frame->data[0][offset + 0] = 0; // B
  
          frame->data[0][offset + 1] = 255; // G
  
          frame->data[0][offset + 2] = 0; // R
  
      }
  
      else {
  
          frame->data[0][offset + 0] = 255; // B
  
          frame->data[0][offset + 1] = 0; // G
  
          frame->data[0][offset + 2] = 0; // R
  
      }
  
  }

  then i have this video output :

  

  and i had this options for ffmpeg :

  codec : libx264rgb
  & pix_fmt : AV_PIX_FMT_BGR24

  in fact i expect something like this video output :

  

  i’m also new in ffmpeg and i realy dont know advanced stuffs about video encoding ,so anybody knows what is problem ?

• How to segment audio and video to the same segments number ?

  24 décembre 2019, par julian zapata

  I’ve extracted audio and video from the same mp4 file and created different variants for different resolutions. When I segment the videos and the audio file with MP4Box, the video segments are the same segments number but the audio segments have one more. I need the video and audio segments to be the same number to use with dash.

  I’m using the next commands to produce the video and audio files :

  Command to extract the audio from mp4 file :

  ffmpeg -y -i "transformers.mp4" -c:a aac -b:a 192k -vn "transformers_audio.m4a"

  Produce each variant of the video with the next command modifying the resolution and bitrate parameters :

  ffmpeg -i transformers.mp4 -c:v libx264 -r 24 -x264opts "keyint=48:min-keyint=48:no-scenecut" -an -vf scale=640:360 -b:v 750k -dash 1 transformers_640x360_750k.mp4

  Generate the mpd file and segment the videos and audio each 4 seconds with :

  mp4box -dash 4000 -profile "dashavc264:live" -bs-switching no -sample-groups-traf \ 
  
  -out output4\ 
  
  transformers.mpd \ 
  
  transformers_480x270_400k.mp4 \ 
  
  transformers_640x360_800k.mp4 \ 
  
  transformers_960x540_1200k.mp4 \
  
  transformers_1280x720_1500k.mp4 \ 
  
  transformers_1920x1080_4000k.mp4 \
  
  transformers_audio.m4a

  This produces 36 segments for each variant of the video and 37 for the audio. How to solve this little variation ? How to make the audio segments number exactly the number of video segments ?

• Is this the best way to decrease the number of failures when downloading m3u8 ?

  26 juillet 2022, par zackchess1

  I have a bunch of m3u8 links that I am trying to download.

  


  When I use ffmpeg, I get an average of 8/10 videos. The remaining 2 videos simply don't download. I use this command :

  


  ffmpeg -i http://.../playlist.m3u8 -c copy -bsf:a aac_adtstoasc output.mp4

  


  I have seen suggestions to use yt-dlp and aria2c to reduce the number of failures. Do either of these actually affect failure rates ?

  


  Would you suggest using :

  


  yt-dlp M3U8LINK

  


  OR

  


  yt-dlp --downloader aria2c M3U8LINK

  


  IF NOT, WHAT COMMAND DECREASES THE NUMBER OF FAILURES ? Thanks.